Sjöström Audio

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This project is in my head at the moment and some of it is in my computer. Some background can be found in my JSR-01 project.

This design is based on my QSXPS project as base with the topology from the JSR-01 project and the goal was to make the pcb with hole mounted parts except for the opamps which are doubled with pads for SO08 opamps. This means that you can choose almost any opamp.

Interesting features

  1. Extremely low noise.
  2. Very low output impedance in the audioband.
  3. Easy to change voltage, also to negative voltage but this particular design (pcb) requires two different pcb's, one for positive voltages and one for negative (not made yet).
  4. Well-known and well-tested in serious applications.
  5. Option for TO220 and TO126 transistors, the pass transisitor mounted on a heatsink on the pcb or an external.
  6. Option for a pre-regulator LM317/337 mounted on a heatsink on the pcb or an external.
  7. LM431 reference but I have made markings for anode, cathode and reference so it will be easy to mount any other 2- or 3 pin device like LM329.
  8. Trimpot for both reference and feedback in order to trim the output voltage easily.
  9. Short circuit protection via a PTC fuse and/or with a shunt and a transistor. The latter is more safe but will increase the output impedance somewhat. I recommend only the PTC fuse.
  10. All resistors 10 mm so it is possible to use a cut and bending machine for those parts.
  11. High output current, max 1-3 A but tests will determine how much. 1 ampere is garanteed.
  12. Nice looking pcb with double ground planes and very thick copper, 95 um.
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